*If you're doing this chain for twink gear, then make sure to pick up Diabolical Plans, which drops from the mobs in the same area as the felfire. The next quest in that chain, Never Again!, rewards BiS rings for most classes @19/20. The best time to do that quest is just after you've picked up All Apologies (so you can hearthstone to Orgrimmar once you've got the 2 weapons, talk to Hellscream, then fly back to get Durak's head).

Also, you may as well pick up Destroy the Legion from Valusha at the same time as Playing With Felfire, for a bit more gold, as you'll be killing the demons anyway.